An NSImage extension that converts an NSImage in ANY supported format to a new NSImage using the generic RGB colorspace.

NSImage+copyAsRGBA.swift

extension NSImage {
  
   /// An NSImage extension that converts an NSImage in ANY format to a new NSImage using the calibrated RGB colorspace.
   ///
   /// Useful when you have to support a 3rd party tool that has format limitations, such as not supporting 
   /// paletted PNG files or grayscale colorspaces (I'm looking at you Create ML!)
   func copyAsCalibratedRGBColorspace() -> NSImage? {
      guard let rep = self.representations.first else {
         return nil
      }

      let origSize = NSSize(width: rep.pixelsWide, height: rep.pixelsHigh)
      let newRect = NSRect(x: 0, y: 0, width: origSize.width, height: origSize.height)

      guard let representation =
         NSBitmapImageRep(
            bitmapDataPlanes: nil,
            pixelsWide: Int(newRect.width),
            pixelsHigh: Int(newRect.height),
            bitsPerSample: 8,
            samplesPerPixel: 4,
            hasAlpha: true,
            isPlanar: false,
            colorSpaceName: .calibratedRGB,
            bytesPerRow: 0,
            bitsPerPixel: 0
         ) else {
            return nil
      }

      representation.size = newRect.size

      NSGraphicsContext.saveGraphicsState()
      NSGraphicsContext.current = NSGraphicsContext(bitmapImageRep: representation)
      rep.draw(in: newRect, from: .zero, operation: .copy, fraction: 1.0, respectFlipped: true, hints: nil)
      //self.draw(in: newRect, from: NSZeroRect, operation: .copy, fraction: 1.0)
      NSGraphicsContext.restoreGraphicsState()

      let newImage = NSImage(size: newRect.size)
      newImage.addRepresentation(representation)

      return newImage
   }
}